naming for asset maintenance task should be task name (#14607)

diff --git a/erpnext/assets/doctype/asset_maintenance_task/asset_maintenance_task.py b/erpnext/assets/doctype/asset_maintenance_task/asset_maintenance_task.py
index 2a5666d..d98cc31 100644
--- a/erpnext/assets/doctype/asset_maintenance_task/asset_maintenance_task.py
+++ b/erpnext/assets/doctype/asset_maintenance_task/asset_maintenance_task.py
@@ -7,4 +7,5 @@
 from frappe.model.document import Document
 
 class AssetMaintenanceTask(Document):
-	pass
+	def autoname(self):
+		self.name = self.maintenance_task